For performing hard coating on the surfaces of electronic/electric devices or various plastic materials for imparting scratch resistance or the like thereto, compositions containing an energy ray-curable resin and hard (especially having a Mohs hardness of 6 or more) inorganic microparticles have heretofore been investigated.
The UV-curable resin concretely described in PTL 1 contains, for the purpose of protecting the display surface of liquid-crystal displays, a polyfunctional urethane acrylate, surface-treated silica microparticles that have been prepared by introducing a reactive group into the surfaces of microparticles of colloidal silica by methacrylic acid or the like, and a relatively large amount of an organic solvent. On the other hand, PTL 2 describes use of a UV-curable resin that contains zinc antimonate microparticles for antistatic, a dispersant, a polyfunctional acrylate compound such as dipentaerythritol hexaacrylate, and an organic solvent such as toluene. In this, “a dispersant of an ethylene oxide (EO)/propylene oxide (PO) adduct of an amine” is said to be an indispensable component (claim 1).
On the other hand, PTL 3 describes preparation of “a curable composition prepared by blending a silica-based polycondensation product (a) obtained through two-stage hydrolysis and polycondensation, in the presence of colloidal silica having a mean particle size of 1 to 100 nm, of a γ-methacryloyloxypropyltrimethoxysilane or the like (a-1) and a phenyltrimethoxysilane or the like (a-2), a polyfunctional (meth)acrylate (d) and an initiator (e)”, and carrying out “each reaction for the production at 45 to 100° C. for 3 to 24 hours” (abstract). In Examples in PTL 3, one prepared by adding bis(4-methacryloyloxyethoxyphenyl)propane and triethylene glycol dimethacrylate to a liquid in which the “silica-based polycondensation product (a)” is dispersed in an organic solvent, followed by distillation of volatile components under reduced pressure is used as a curable composition.
On the other hand, PTL 4 proposes one containing an alkylene oxide-modified dipentaerythritol (meth)acrylate as an energy ray-curable resin for use for a resist resin or the like. On the other hand, PTL 5 shows “an active energy ray-curable composition for hard coating, characterized by containing silica whose surface has been hydrophobized, and a dispersant prepared by reacting a (meth)acrylic acid-(meth)acrylic acid ester copolymer with 3,4-epoxycyclohexylmethyl (meth)acrylate” (abstract). PTL 6 describes producing an organic solvent-dispersed silica sol, then dispersing it in an ester-modified epoxy resin and thermally curing it.